Mobile Fundamentals · SIMs & Identity · Lesson 5 of 5

Challenge: The Secondhand Phone

Vet a used phone for your aunt, then help her through a SIM swap.

Before you pay

Your aunt Rosa wants to replace her old phone. She has found a used Android phone listed online and is meeting the seller at a coffee shop. She asked you to come along and make sure the deal is safe.

Rosa plans to keep her current carrier and her phone number, and simply move her SIM card into the new phone. After a scare last year, she also wants her bank account better protected.

At the coffee shop, the seller hands over the phone. Before Rosa pays, you want to check that it hasn't been reported lost or stolen. The seller offers to text you his phone number "so you can check everything with that."

His phone number won't help. You need a different number, and you can get it from the phone itself.

A stubborn SIM

The blocklist check comes back clean, and Rosa buys the phone. In the excitement, nobody thinks to ask about anything else.

At home she moves her SIM card from her old phone into the new one. An error message about the SIM appears, and the phone won't make calls or send texts. Everything else seems fine. It joins her home Wi-Fi, apps install, and the camera works. Her SIM still works perfectly when she puts it back in her old phone.

No service

A few weeks later, the phone is unlocked and working well. Then one afternoon Rosa's phone suddenly shows no service. Her husband's phone, on the same carrier and in the same room, has full bars.

Ten minutes later an alert arrives over Wi-Fi. The password on her email account has just been changed, and Rosa didn't change it.

She is panicking. She wants to wipe the phone right away, because she thinks someone has copied her photos and files.

Better than a text

With the carrier's help, Rosa gets her number back. She sets a PIN on her carrier account and turns on the carrier's number-transfer lock.

Now she's looking at her bank's security settings. The bank offers several ways to confirm a new login, and she wants the one that a future SIM swap can't defeat. She's tempted by the longest code, since it sounds the hardest to guess.